The Delaware is a fun one. Your Delaware hen has both silver and is barred. Her basic white body hides the barring but if you look closely at her black pattern feathers you should be able to see the barring. It’s more noticeable on the Delaware roosters because they have more black pattern feathers.
Usually Delaware are used to make red sex links using roosters pure for gold. I did that using a Speckled Sussex rooster. There is a clear difference in the yellow male chicks and the fairly dark red females. Here is a photo of the rooster from that cross. You can see the barring in the darker feathers but the white masks the barring on the body.
Your Blue Copper Maran should be pure for gold so mixed with the silver you’d think you could make red sex link chicks but it doesn’t work that way. I’m not exactly sure why but I think the birchen in the rooster gets in the way of the gold/silver expressing itself in the chick down. I think you will see it in the adult plumage where a pullet will have red where the cockerel will have more yellow or what I call rusty white, but if it doesn’t show up in the down you can’t use it. That’s if any red or yellow comes through at all. Looking at that chick I’m not sure any red or yellow will come through but I’ve been surprised in the difference in down color, juvenile plumage colors and patterns, and final adult plumage colors and patterns before.
If you look at Tadkerson’s charts for making red or black sex links, the Copper Maran, either black or blue, does not show up.
But with the Delaware hen being barred and the Blue Copper Maran rooster not being barred, any chicks you get that are barred are male and any that are not barred will be female. I’m not sure if the spot will show up properly in the down but the barring will show up in the juvenile feathers.
I don’t know all the breeds that are barred. Tadkerson lists a very few that with any of the roosters on the left of his chart can be relied on to make black sex links. It’s highly possible other breeds of hens could be used to make black sex links, but it may take a very special rooster so you can see the spot. Those breeds just might not fit on a generic chart.
You don’t even need a purebred hen or a black hen to make black sex links. You just need a hen that is barred, a rooster that is not barred, and the genetics in both to make the spot show up in the down.